How to use the httpx.PoolLimits function in httpx

async def test_soft_limit(server):
    """
    The soft_limit config should limit the maximum number of keep-alive connections.
    """
    pool_limits = httpx.PoolLimits(soft_limit=1)

    async with ConnectionPool(pool_limits=pool_limits) as http:
        response = await http.request("GET", server.url)
        await response.read()
        assert len(http.active_connections) == 0
        assert len(http.keepalive_connections) == 1

        response = await http.request("GET", "http://localhost:8000/")
        await response.read()
        assert len(http.active_connections) == 0
        assert len(http.keepalive_connections) == 1

def test_limits_repr():
    limits = httpx.PoolLimits(hard_limit=100)
    assert repr(limits) == "PoolLimits(soft_limit=None, hard_limit=100)"

def test_limits_eq():
    limits = httpx.PoolLimits(hard_limit=100)
    assert limits == httpx.PoolLimits(hard_limit=100)

async def test_pool_timeout(server):
    pool_limits = httpx.PoolLimits(hard_limit=1)
    timeout = httpx.Timeout(pool_timeout=1e-4)

    async with httpx.Client(pool_limits=pool_limits, timeout=timeout) as client:
        async with client.stream("GET", server.url):
            with pytest.raises(httpx.PoolTimeout):
                await client.get("http://localhost:8000/")

def test_limits_eq():
    limits = httpx.PoolLimits(hard_limit=100)
    assert limits == httpx.PoolLimits(hard_limit=100)

def setup_session(proxy: Optional[str], concurrency: int):
  s = httpx.AsyncClient(
    pool_limits = httpx.PoolLimits(
      soft_limit = concurrency * 2,
      hard_limit = concurrency,
    ),
    timeout = httpx.Timeout(20, pool_timeout=None),
    headers = {'User-Agent': DEFAULT_USER_AGENT},
    http2 = True,
    proxies = proxy,
  )
  session.set(Session(s, concurrency))

def get(self, *args, **kwargs) -> ResponseManager:
    proxy = kwargs.pop('proxy', None)
    client = self.clients.get(proxy)
    if not client:
      client = httpx.AsyncClient(
        pool_limits = httpx.PoolLimits(
          max_keepalive = self.concurrency * 2,
          max_connections = self.concurrency,
        ),
        timeout = httpx.Timeout(20, pool_timeout=None),
        headers = {'User-Agent': DEFAULT_USER_AGENT},
        http2 = True,
        proxies = proxy,
      )
      self.clients[proxy] = client
    return ResponseManager(client, args, kwargs)